The V8 cars are probably more than likely a better starting point. He's right about getting a left over '10 you could probably get a good deal on one.
If you're seriously going to rip the motor out and figure out to wedge a big block in there, the smaller V6brakes might be a better option for drag wheels, but beyond that it depends on how serious you are and how much power and what your goals are going to be to determine which would be a better "starting" platform.
Im assuming you wouldn't use factory exhaust either way so that wouldnt matter. You'll probably have to do re-do everything suspension, motor, tranny, rear end, all that **** anyway if you're going with a big block...which doesn't make all that much sense to me with cost-effectiveness in mind. That would be one hell of an expensive build.